SH2-170 has been described in the past a seldom imaged but I think that has changed. I had to sort through 3 pages of Google results - all were amatuers like us - before I found it described on the Italian Wikipedia. Maybe we should now say often imaged and seldom researched!
The most interesting insight is that the entire nebule is believed to be ionized by a single main sequence star. I presume this star carved itself out of the hydrogen cloud to produce the central void. That is not address however.
From Wikipedia.it:
"Sh2-170 is a H II region located on the Arm of Perseus about 2300 parsecs (about 7500 light years ) away, [2] near the edge of a large superbubble originating from the combined action of the stellar wind of the Cassiopeia stellar association OB5 . [4] The person [sic] responsible for the ionization of its gases is known by the initials BD + 63 2093; it is a main sequence star with spectral class O9V, part of the small and young open clusterStock 18. The edges of the ionized region are mostly blurred, indicating a lower density at the periphery, except for the south-eastern side; the ionizing star is located near the center, on the leading edge of a small isolated molecular cloud . It is believed that 40% of the mass of the complex consists of monoatomic neutral hydrogen ( HI ), located beyond the ionization front."The processing here has become a bit of a habit for me with Narrowband images:
1) Create starless with StarXterminator
2) Create a factor image using the starless OIII master, stretched, heavily de-noised with a steep "S" curve applied
3) Use the factor image in a dynamic narrowband blend in Pixelmath
4) Use the Ha data as Luminance
5) Create an RGB image for stars and separate out the stars
6) Stretch the stars being sure to retain the clipped background
7) Layer the RGB stars over the narrowband image using a Screen mode blend in PS
8) Make the usual enhancements and tweaks to taste in PS
9) Do a final NoiseXterminator run
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